docs: def callfunc(self, argv=None):
          """
          Parse the argv list and extract a dictionary of arguments which
          is then passed to  the function underlying the script.
          """
          if not self.checked:
              self.check_arguments()
              self.checked = True
          namespace = self.parentparser.parse_args(argv or sys.argv[1:])
          return self.func(**vars(namespace))